(Image: EBM Pyramid and EBM Page Generator, copyright 2006 Trustees of Dartmouth College and Yale University. All Rights Reserved.
Produced by Jan Glover, David Izzo, Karen Odato and Lei Wang.)
Study designs are placed into a hierarchy based on their reliability (probability of bias) known as the Levels of Evidence.
The Levels of Evidence are often represented by a pyramid, with the highest levels of evidence (least common) near the top, and the lowest levels of evidence (most common) near the bottom. The pyramid above is based on the Oxford Centre for Evidence Based Medicine's rating system for therapeutic studies, but a variety of rating systems exist.
Some study designs are better suited to answer certain types of questions. Identifying the clinical domain your question falls under can help determine what study designs to look for in order to find the best, most suitable evidence. Systematic Reviews and Meta-Analyses are always preferred.
Check off the clinical domain and preferred study design type on the Well-Built, Patient-Oriented Clinical Question worksheet. The link to that worksheet can be found above.
Preferred Study Design (after systematic reviews and meta-analyses)
|Cross-Sectional Studies or Gold Standard
|Etiology or Prognosis
|Cohort > Case-Control > Case Series
|Randomized Controlled Trial > Controlled Trial > Cohort > Case-Control
|Quality of Life
|Randomized Controlled Trial > Controlled Trial or Quasi-Experimental Studies
Click "Next" to learn about the Acquire Step.